Association of TP53 mutation with decreased prevalence of MSI-high, RAS and PI3KCA mutations in metastatic colorectal cancer.

Abstract

e15578 Background: TP53 tumor suppressor gene is mutated in approximately 50% of colorectal cancer (CRC). How TP53 mutations are associated with the prevalence of the other common genomic alterations such as RAS (KRAS/NRAS), BRAF, PI3KCA, as well as microsatellite stability (MSI) is not clear. Methods: We investigated the impact of TP53 mutations on other common genomic alterations and survival in patients with metastatic CRC using the NGS data within Kaiser Permanente Northern California (KPNC). Results: From November 2017 to January 2021, genomic profiling was performed on 1056 patients with metastatic CRC, of whom 740 patients harbored a TP53 mutation (TP53mut) and 316 patients had wild-type TP53 (TP53wt). We found that median overall survival (OS) was similar between the TP53wt and TP53mut patients (50.1 vs 47.5 months, p = 0.9), however, the percent with a Ras mutation was significantly higher in patients with TP53wt compared to TP53mut (63.2 vs 45.2%, p = 0.0001). Interestingly, the percent with MSI-high was also significantly higher in TP53wt than TP53mut patients (11.1 vs 1.4%, p = 0.0001), however, the response rate of the MSI-high patients to immune checkpoint inhibitor (ICI) was similar (40 vs 37.5%). In addition, a significantly higher percent of patients with TP53wt had PI3KCA mutations and a significantly lower percent had c-Myc amplifications compared to patients with TP53mut (PI3KCA, 32 vs 10.7%, p = 0.0001; c-Myc, 1.26 vs 4.6%, p = 0.008). There was no significant difference in the percent of BRAF mutations between the two patient populations (6.2 vs 9.8%). A significantly higher percent of patients with TP53wt and a PI3KCA mutation had a Ras mutation compared to patients with TP53mut and a PI3KCA mutation (81.2 vs 57%, p = 0.0004). However, TP53 mutation status was not significantly associated with the OS of patients with either a Ras, or BRAF, or PI3KCA mutation, or combination of Ras and PI3KCA mutations. Conclusions: TP53 mutation is associated with decreased prevalence of Ras, PI3KCA mutation and MSI-high in patients with metastatic CRC, however, without impacting the OS or response rate to ICI.